A known inkjet printer includes a print head and a purging mechanism. The print head has nozzles configured to eject ink supplied from a tank. The purging mechanism is configured to forcibly discharge ink from the nozzles. The inkjet printer may use pigment ink in which pigments are suspended or dispersed in a solvent.
The pigment ink has advantages, e.g., excellent color strength, and disadvantages, e.g., pigment settling. The pigments may settle at a bottom or a lower end of the tank during periods of storage or non-use. Such pigment settling may cause a portion of the pigment ink at the bottom of the tank to be locally concentrated or enriched and become viscous. The viscous ink supplied to the print head may clog the nozzles.
One solution to this problem is to discharge the concentrated ink out of the tank by executing a purge operation. For the purge operation, the inkjet printer determines an amount of ink consumed by the print head during a predetermined period of time. When the amount of ink consumed is less than the predetermined amount, the inkjet printer controls the purge mechanism to discharge or purge, through the nozzles, a particular amount of ink that varies depending on the amount of ink consumed. However, the inkjet printer may discharge too much ink during the purge operation.